Various types of messaging systems exist that enable the exchange of digital messages from a message author to one or more recipients. Examples of such messaging systems include electronic mail (e.g., email or e-mail), instant messaging, and text messaging. Some messaging systems, including email, operate across the Internet or other computer network(s). Many messaging systems are based on a store-and-forward model, where a messaging server accepts, stores, and delivers messages. In such systems, neither the sender nor recipient needs to be online simultaneously.
In the vast majority of messaging systems, messages are immediately available for consumption as soon as they are provided by the message author. In other words, as soon as the messaging server receives a message, the messaging server transmits the message to the recipient(s) with as little delay as possible.